The present invention relates to thrust reversers for jet engines, and more particularly, to anti-deployment mechanisms for thrust reversers.
Jet aircraft, such as commercial passenger and military aircraft, utilize thrust reversers on the aircraft""s jet engines to reduce the aircraft""s speed after landing. One type of thrust reverser used in modem jet aircraft is the cascade type, described in more detail in U.S. Pat. No. 5,448,884. For ease of reference, the description of the cascade type of thrust reverser is substantially reproduced herein.
Referring first to FIG. 1, there is shown a conventional aircraft nacelle indicated at 18 which includes a jet engine, such as a Pratt and Whitney PW4000, indicated at 20 (shown in hidden lines) supported by a strut 22 on a wing 24 (only a portion of which is shown). The nacelle 18 includes a nose cowl 26, a fan cowl 27, a thrust reverser sleeve 28, a core cowl 30 and nozzle exhaust 32. Although some of these components are made up of two mirror image parts split vertically in a clamshell arrangement, each component will be referred to herein as being one piece.
As shown in more detail in FIGS. 2 and 3, the thrust reverser system includes an inner duct (fan duct cowl) 36 and outer sleeve 28. The sleeve 28 translates in an aft direction indicated by an arrow identified by a number 42 in FIG. 2, and a forward direction indicated by an arrow identified by a number 44. When the thrust reverser is deployed, the translating sleeve 28 moves aft from a xe2x80x9cstowedxe2x80x9d position shown in FIG. 1 to a xe2x80x9cdeployedxe2x80x9d position shown in FIG. 2. In this process, cascade vanes 46 (FIG. 2) mounted to a thrust reverser support structure are uncovered. Vanes 46 are slanted in a forward direction so that during thrust reverser operation, fan air from the engine is redirected forward through the vanes (indicated by arrows 47) to aid in decelerating the airplane.
Air driven aft by the engine fan flows along an annular duct 48 (FIGS. 2 and 3) formed by the fan duct cowl 36 and core duct cowl 30. Movement of the sleeve 28 in the aft direction, causes blocker doors 50 to pivot from their stowed positions (shown in FIG. 3) to their deployed positions (shown in FIG. 2) where the doors are positioned to block rearward movement of the air through duct 48. In this manner all rearward movement of the engine fan air is redirected forward through the cascade vanes 46.
Movement of the sleeve 28 is guided along a pair of parallel tracks mounted to the top and bottom of the fan duct cowl 36 in a fore and aft direction. The sleeve 28 is moved between the stowed and deployed positions by means of a number of hydraulic actuators indicated at 54 (FIG. 3), each having an actuator rod 56 which is connected to the sleeve 28. More specifically, as shown in FIGS. 5 and 6, each actuator 54 is connected to a structural torque box 57 via a gimbal mount 61 thereby allowing the actuator to accommodate lateral variances in sleeve motion. As shown in FIG. 4, the actuator rod 56 is located inside the aerodynamic surface of sleeve 28 and is connected to the sleeve 28 by a ball joint 68. The ball joint 68 is accessible by removing a panel 70 which is bolted to the exterior surface of the sleeve 28.
In operation, when the thrust reverser is commanded by the pilot to the deployed position, each actuator rod 56 (FIG. 5) extends in the aft direction. Conversely, when the thrust reverser is commanded by the pilot to move to the stowed position, each actuator rod 56 retracts in the forward direction. In an exemplary embodiment, the actuator 54 is a thrust reverser actuator currently installed on Boeing 767 airplanes.
As shown in FIG. 7, each actuator 54 includes a double acting piston 72 which is extended in the rightward direction (with reference to FIG. 7) by hydraulic pressure acting against a face 74 of the piston 72. Retraction of the piston 72 and the thrust reverser sleeve therewith is accomplished by relieving hydraulic pressure from the piston face 74, so that hydraulic pressure acting against an opposing face 76 of the piston causes it to move in the leftward direction. The piston 72 is connected to the actuator rod 56 which in turn is connected to the thrust reverser sleeve 28 in the manner described previously.
In the exemplary embodiment, each thrust reverser sleeve is driven by three of the actuators 54 (FIG. 3). It is important that each actuator 54 extend and retract the sleeve at the same rate to avoid causing the sleeve to bind along the tracks 51. To accomplish this, operation of each of the three actuators 54 is synchronized by means of an interconnecting synchronizing shaft 80. The sync shaft 80 (FIGS. 5 and 6) is a tube having a stationary outer sleeve and an internal rotating flexible shaft 81 which synchronizes motion of the three actuators. The outer sleeve of the sync shaft 80 is connected to the actuator 54 by a swivel coupling 82.
In order to explain this synchronizing operation in greater detail, reference is made to the section view of the actuator 54 in FIG. 7. As shown, the piston 72 is connected via a non-rotating threaded drive nut 84 to a rotating Acme screw 86. As piston 72 translates the drive nut 84 moves with it. Translating movement of the drive nut 84 along the Acme screw 86 causes the Acme screw to rotate thereby converting translational movement into rotational movement. Synchronizing operation is further accomplished by a worm gear 90 (FIG. 6) located inside the actuator housing which engages a spur gear 94 which in turn is mounted to the end of the Acme screw 86. Furthermore, the internal sync shaft 81 has a splined end tip which is positioned inside a slot (not shown) in the right end of the worm gear 90.
Referring again to FIG. 7, extension and retraction of the thrust reverser sleeve results in rotation of the Acme screw 86 and rotary gear 94 therewith. This causes rotation of the worm gear 90 in a manner that a high torque and low rotational speed input from the Acme screw 86 is converted by the worm gear 90 to a low torque and high rotational speed output to the sync shaft. In the event one of the actuators 54 attempts to move the thrust reverser sleeve at a different rate than the other actuators, their rates are equalized via the common sync shaft and through the respective worm gears, spur gears and Acme screws of the actuators. This results in uniform translation of the thrust reverser sleeve.
In order to allow the thrust reverser sleeve 28 to be moved between the stowed and deployed positions for maintenance purposes while the airplane is on the ground, a manual drive clutch mechanism 96 shown in FIG. 6 is attached to the left end of the actuator. The manual drive clutch 96 includes a socket (not shown) for receiving a square drive tool (also not shown) in its left end 95. The manual drive clutch 96 is connected by a female coupling 97 to a threaded male connector 98 at the left end of the actuator. The drive clutch 96 includes a drive shaft 99 (FIG. 10) having a square-ended tip which extends in a rightward direction from the clutch and which fits inside an end slot 100 (FIG. 5) of the actuator worm gear 90.
In operation, when the square drive tool is inserted into the manual drive clutch in a rightward direction, the clutch is engaged thereby allowing the square drive tool to drive the worm gear 90 (FIG. 6), which in turn drives the spur gear 94, Acme screw 86 to translate the thrust reverser sleeve.
With reference to FIGS. 8-11, mechanical lock 104 is connected to the actuator 54 in place of the drive clutch 96. In turn, the drive clutch 96 is connected to the left end of the mechanical lock 104. Like elements described previously will be identified in FIGS. 8 through 11 by like numerals.
The purpose of the mechanical lock 104 is to prevent uncommanded translation of the thrust reverser sleeve. The mechanical lock 104 includes a cylindrical housing 106 (FIG. 10) having an internal cylindrical passageway 108. Axially aligned with the centerline of the passageway 108 is a cylindrical shaft 110 having an eight-pointed splined slot 112 at its left end for receiving therein the splined end tip 99 of the clutch mechanism 96 described previously. At the right end of the shaft 110 is a splined tip 113 which is inserted in the socket 100 (FIG. 5) of the actuator worm gear 90. Mounted centrally on the center shaft 110 (FIGS. 9 and 10) is a lock wheel 114 having a cylindrical outer surface 116.
Extending from the locking wheel surface 116 at equally spaced intervals are four square teeth 118 (FIG. 11) whose rotational path is blocked by a locking pin 120 when the device is de-energized and the locking pin is in a down/locking position shown in FIGS. 10 and 11. More particularly, the locking pin 120 extends through an opening 122 in the upper wall of the housing 106. It should be appreciated that the direction of the shear force created by the rotation of the locking wheel 114 and shaft 110 therewith is orthogonal to the locking/unlocking movement of the locking pin thereby minimizing the forces required to extend and retract the locking pin 120.
In operation, when the locking pin 120 is in the down/locking position it prevents rotational movement of the shaft 110 thereby preventing rotation of the worm 90 (FIG. 9), worm gear 94, and the Acme screw 86. This, in turn, prevents translational movement-of the drive nut 84 (FIG. 7), the piston 72 and the thrust reverser sleeve 28 therewith, thereby preventing thrust reverser sleeve motion.
Movement of the locking pin 120 (FIG. 10) between the locked position and an unlocked position (where the pin 120 is above and clear of the teeth 118) is controlled by an electrically operated solenoid 124 through which the upper end of the locking pin 120 extends. Electrical control is initiated at the cockpit (not shown) via conventional airplane thrust reverser control circuits and is transmitted by electrical wires 125 to the solenoid 124. Control of the solenoid may be accomplished in a conventional manner. It should be appreciated that other means for controlling movement of the locking pin 120, such as hydraulic or electrohydraulic means, may be utilized.
Thrust reversers include various anti-deployment mechanisms to prevent in-flight deployment, such as locking actuators, non-locking actuators, synchronization shaft locks (sync lock), and auto-restow systems. Thrust reversers presently used on Boeing aircraft have three levels of locking means. For example, thrust reversers used on wide body aircraft illustratively have two locking actuators per nacelle and one sync lock per nacelle. Thrust reversers used on narrow body aircraft illustratively have one locking actuator per nacelle, one sync lock per nacelle, and an auto-restow system per nacelle.
It is an object of this invention to link the synchronization systems of the thrust reverser actuation systems of the two sides of the thrust reverser so that anti-deployment mechanisms used for each of the thrust reverser actuation systems can provide one or more of the redundant anti-deployment mechanisms for the other thrust reverser actuation system.
A synchronization cross-feed system for a thrust reverser having at least first and second sides. Each side of the thrust reverser has a thrust reverser actuation system having a plurality of actuators. The actuators in each thrust reverser actuation system are synchronized by a synchronization system. A synchronization cross-feed system couples the synchronization systems of the thrust reverser actuation systems of the first and second sides of the thrust reverser allowing an anti-deployment mechanisms of each thrust reverser actuation system to serve as one or more of the redundant anti-deployment mechanisms for other the thrust reverser actuation system.
In an embodiment, the synchronization cross-feed systems has first and second coupling assemblies that are removably coupled to each other so that they decouple from each other when the thrust reverser sides are opened to allow the thrust reverser sides to be opened.
In an embodiment, the first and second coupling assemblies have engagement teeth that mate with each other when the thrust reverser sides are closed.
In an embodiment, the engagement teeth of the first coupling assembly is disposed on a telescopic coupling shaft that is spring loaded by a spring in the first coupling assembly that forces telescopic coupling shaft toward the second coupling assembly.
In an embodiment, the first and second coupling assemblies have shafts that are coupled to respective actuators of the thrust reverser actuation systems of the first and second thrust reverser sides.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.